Safety interlock system for medical fluid pumps

ABSTRACT

A medical fluid delivery set is provided with a magnetic field source in the region of its mounting to a fluid flow control apparatus. The flow control apparatus includes a magnetic field sensitive switching component which detects the proper placement of the delivery set on the flow control apparatus and prevents operation of the fluid delivery system unless a set is in proper position.

BACKGROUND OF THE INVENTION

This invention relates to fluid delivery systems for providingperenteral nutrition, enteral nutrition or other fluids to patients whorequire infusion of fluids. The invention is particularly related toimprovements in such systems which use a disposable fluid delivery setin conjunction with a fluid flow control unit, such as a pump motor set,for supplying such fluids to a patient at a controlled delivery rate.

The assignee of the present invention presently markets an enteraldelivery system under the trade name "Kangaroo". The system includes afluid delivery motor set and a disposable fluid delivery set, whichincludes a fluid tube, a drip chamber which is arranged to be mounted torecess on the motor set, a mounting member, also arranged to be mountedto a recess on the motor set, an outlet tube connected to the mountingmember and a pump tube which connects the drip chamber to the mountingmember and engages a motor driven rotor on the motor set to form aperistaltic pump.

In the Kangaroo enteral delivery system the engagement of the pump tubeto the rotor controls the flow of fluid to the patient according to thespeed of the rotor. In the event the delivery set is not properlymounted to the motor set and the pump tube is not firmly engaged withthe rotor, an excess flow of fluid through the set can occur under forceof gravity. Improper mounting of the drip chamber is unlikely because ofthe mechanical configuration of that component and its correspondingrecess. Improper placement of the mounting member, e.g. below, above oroutside of the receiving recess, is possible if the delivery set isinstalled on the motor set by an operator who has not received properinstruction in the operation of the system. Instances of such improperinstallation have been reported.

It is an object of the present invention to provide an interlock systemwhich prevents operation of a fluid delivery system unless the deliveryset is properly placed and installed on the flow control unit.

SUMMARY OF THE INVENTION

The present invention is applicable in a medical fluid delivery systemwhich includes a fluid delivery set arranged to be mounted on acorresponding fluid delivery flow control apparatus. According to theinvention there is provided a method for preventing improper systemoperation which comprises the steps of providing a switching componenton the flow control apparatus which has a first electrical state whenthe delivery set is properly mounted to the flow control apparatus and asecond electrical state when the delivery set is not properly mounted tothe flow control apparatus. According to the invention operation of theflow control apparatus is enabled in response to the first electricalstate and disabled in response to the second electrical state. Thesecond electrical state will also cause an alarm to be activated whenoperation is attempted.

According to the invention there is provided a fluid flow controlapparatus which is arranged to receive a corresponding fluid deliveryset. The fluid flow control apparatus is provided with a switchingcomponent responsive to proper mounting of a fluid delivery set and isprovided with control means responsive to the switching component forpermitting operation of the flow control apparatus only when theswitching component detects proper mounting of the fluid delivery set.Preferably the switching component is a magnetic field sensitivecomponent.

In accordance with the invention there is provided a disposable medicalfluid delivery set arranged to be mounted to a fluid flow controlapparatus which is arranged for operating with portions of the set forcontrolling the rate of fluid delivery. According to the invention thereis provided an improvement comprising a magnetic field source on thefluid delivery set, the source being arranged in a position on the setwhich corresponds to a magnetic field sensitive component on the controlapparatus. In a preferred embodiment the fluid delivery set includes atleast one mounting member arranged for attachment to a correspondingreceiving member on the control apparatus and the magnetic field sourceis mounted on the mounting member.

For a better understanding of the present invention, together with otherand further objects, reference is made to the following description,taken in conjunction with the accompanying drawings, and its scope willbe pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is perspective view of a medical fluid delivery systemincorporating the present invention.

FIG. 2 is a perspective view of the interior of the medical fluiddelivery system of FIG. 1.

FIGS. 3A, 3B, 3C and 3D are detailed illustrations of a portion of theFIG. 1 system illustrating correct and incorrect positioning of a fluiddelivery set.

FIG. 4 is a schematic diagram illustrating the electrical connection ofa switching component in the fluid delivery system of FIG. 1.

FIG. 5 is a top view of a mounting member in accordance with the presentinvention.

FIG. 6 is a cross-sectional view of a mounting member taken along thelines illustrated in FIG. 5.

FIG. 7 is a cross-sectional view of the FIG. 1 fluid delivery systemshowing details of the components of the present invention.

FIG. 8 is plan view of a magnetic field source used in the fluiddelivery system of FIG. 1.

FIG. 9 is a cross-sectional view of a magnetic field source taken alongthe lines illustrated in FIG. 8.

DESCRIPTION OF THE INVENTION

FIG. 1 is a perspective view of an enteral fluid delivery systemincorporating the present invention. The system includes a motor set 10upon which is mounted a disposable delivery set which includes inlettube 18 which is connected to a source of fluid, drip chamber 19 whichis connected to receive fluid from tube 18 and is mounted in recesses 20and 22 on motor set 10. The delivery set also includes a pump tube 16which is connected to the bottom of drip chamber 19 and which surroundsa pump rotor 14 on motor set 10 to form a peristaltic pump. The deliveryset also includes a circular mounting member 24 which is received inmounting recess 26 which connects pump tube 16 to outlet tube 28. Rotor14 on motor set 10 is driven by motor 12 and rotates at various speedsto control the rate of delivery of fluid, such as enteral nutritionfluid, to a patient.

Those familiar with the art will recognize that similar delivery setsand motor sets are used in connection with delivery of other medicalfluids, such as intravenous i.e. perenteral fluids, or blood. In somesystems rather than provide a motor driven pump, as the motor set 10 ofFIG. 1, there is provided a flow control apparatus which controls theflow of fluid by gravity, for example by exerting a valve- like force ona portion of the fluid delivery set.

The present invention is concerned with assuring proper placement of thefluid delivery set onto the motor set or other flow control apparatus,and in particular with the proper placement of the pump tube 16 aroundthe rotor 14 to form a peristaltic pump which provides accurate andcontrolled delivery rates.

Pump tube 16 is mounted to drip chamber 22 at its inlet end and mountedto mounting member 24 at its outlet end. As illustrated in FIG. 1, dripchamber 19 is received in recesses 20 and 22 on motor set 10 andmounting member 24 is received in recess 26. When properly mounted pumptube 16, which is typically silicone tubing is tightly stretched aroundrotor 14 so that the points of rotor contact on tube 16 close thepassage of fluid. Referring to FIG. 3 there is shown in FIG. 3A thecorrect arrangement of the drip chamber and mounting member in therecesses on motor set 10. As shown in FIG. 3A mounting member 24 shouldbe fully received into recess 26. It has come to the inventors'attention that in some cases the mounting member 24 may be improperlyinstalled by inexperienced personnel so that mounting member 24 isseated below recess 26 as shown in FIG. 3B. This arrangement can behazardous to a patient because of excess and uncontrolled flow of fluidthrough the delivery set under force of gravity, whereby fluid isdelivered at a higher rate than properly specified. Another impropermounting of the delivery set is illustrated in FIG. 3C, wherein mountingmember 24 is caught on the lip of recess 26 and not properly seated inthe recess itself. Another improper mounting is shown in FIG. 3D whereinmounting member 24 is not placed completely back into recess 26, butseats on the outer edge thereof.

In accordance with the present invention an arrangement is provided fordetecting the proper placement of mounting member 24 in recess 26.Improper placement of drip chamber 19 is unlikely since it must engageboth recess 20 and recess 22.

In order to detect the proper placement of mounting member 24 in recess26 there is provided a magnetic field source 30 which is a toroidalshaped piece added to mounting member 24 and surrounding the fluidpassage thereof. A magnetic field detector 32 is provided within themotor set 10 and arranged to detect the magnetic field from magneticfield source 30 when mounting member 24 is properly received into recess26. FIGS. 1 and 2 show generally the internal arrangement of motor set10 indicating the placement of magnetic field detector 32 against theinside wall of the motor set adjacent recess 26.

Magnetic field detector 32 is preferably a magneto resistive switchingelement, such as part No. SS21PE, available from Microswitch ofFreeport, Ill. When connected as shown in FIG. 4 this part provides anoutput of plus 5 volts when not in the presence of a magnetic field andzero volts when in the presence of either polarity of magnetic field.The zero or plus 5 volt output signal of switching element 32 isconnected to microprocessor 34 as a digital input signal to cause themotor set 10 to provide an error signal if an operator attempts tooperate the motor set with an improperly placed delivery set. The errorsignal prevents operation of the motor set and preferably causes analarm signal to be provided.

FIG. 5 is a top view of mounting member 24 which is circular incross-section and includes a central passage for fluids. A magneticsource 30 which is toroidal in shape is attached directly to theshoulder of mounting member 24 as shown in the cross-sectional view ofFIG. 6. Magnetic source 30 surrounds an upwardly projecting tubereceiving member 23 which connects to outlet tube 28. Mounting member 24also includes a downwardly extending tube engaging member 25 whichreceives peristaltic pump tube 16. As an alternate to providing aseparate magnetic field source 30, mounting member 24 can be formedentirely from magnetic material.

FIG. 7 shows the details of one arrangement for detecting the presenceof the magnetic element 30 surrounding mounting member 24. The magneticsensitive switching component 32 is arranged on the inside wall of themotor set 10 with its magneto sensitive end pointing at an angle of42.5° toward the magnetic field source 30 mounted on mounting member 24.The end of magnetic sensitive switching element 32 is vertically spaced0.210 inches from the top of magnetic field source 30 and ishorizontally spaced 0.075 inches from the outside diameter of magneticfield source 30. Details of magnetic field source 30 showing mechanicaldimensions are ilustrated in FIGS. 8 and 9.

While it is believed that a wide variety of magnetic materials aresuitable for the magnetic field source, the inventors have found that amaterial composed of 88% stronium ferrite and 12% #6 nylon to be asuitable material. This material is available from Tengan of Ostsego,Mich. the material is magnetized in the axial direction to a magneticstrength of 400 to 500 gauss at the surface edge.

Those skilled in the art will recognize that while the invention hasbeen described with reference to application on an enteral deliverysystem, the present invention is likewise useable in connection withdetecting the proper placement of a disposable delivery set on othermedical fluid delivery systems, such as intravenous pumps or bloodinfusion pumps.

While the present invention has been described with respect to anembodiment which uses a magnetic field source on the disposable deliveryset and a magnetic field sensitive swithing element on the motor set,those skilled in the art will recognize that other arrangements fordetecting the presence of and proper placement of a mounting member onthe motor set are possible, including arrangements of mechanicalmicro-switches on a pump motor set and switch activating devices on thedisposable delivery set.

While there has been described what is believed to be the preferredembodiment of the invention, those skilled in the art will recognizethat other and further modifications may be made thereto withoutdeparting from the spirit of the invention, and it is intended to claimall such changes and modifications as fall within the true scope of theinvention.

We claim:
 1. A medical fluid delivery system comprising;a peristalticpump and a corresponding fluid delivery set operatively mountable onsaid peristaltic pump, a control means on said peristaltic pump forenabling operation of said peristaltic pump, said control meansincluding a means for detecting a predetermined alignment of at least aportion of said fluid delivery set on said peristaltic pump, saidcontrol means enabling the operation of said peristaltic pump inresponse to the detection of said at least a portion of said fluiddelivery set in the predetermined alignment on said peristaltic pump bysaid means for detecting, said fluid delivery set including a magneticfield source mounted in a predetermined position on said fluid deliveryset, and said control means further including a magnetic field sensitivesensor located on said peristaltic pump for detecting said magneticfield source on said fluid delivery set.
 2. The medical fluid deliverysystem of claim 1, wherein said magnetic field source is located on saidfluid delivery set in a predetermined position for detection by saidmagnetic field sensitive sensor on said peristaltic pump when at least aportion of said fluid delivery set is in a predetermined longitudinalalignment on said peristaltic pump to allow fluid delivery by saidperistaltic pump and wherein said magnetic field sensitive sensor doesnot detect said magnetic field source when at least a portion of saidfluid delivery set is not in predetermined longitudinal alignment onsaid peristaltic pump.
 3. The medical fluid delivery system of claim 2,wherein an alarm means is located on said peristaltic pump in operativecommunication with said switching component to activate said alarm meanswhen at least a portion of said fluid delivery is not in predeterminedlongitudinal alignment on said peristaltic pump.
 4. A fluid deliveryapparatus for the delivery of a medical fluid to a patient, comprisingaperistaltic pump having first and second receivers and a rotor thereonfor controlling the rate of fluid delivery to a patient, a fluiddelivery set including a fluid reservoir section, a fluid deliverysection adapted to deliver fluid to a patient and a flexible tubesection adapted to be placed in operative connection with said rotor onsaid pump and first and second mounting members wherein said secondmounting member includes a magnetic field source thereon and said firstand second mounting members are arranged in a predeterminedconfiguration on said delivery set such that when said flexible tubesection is aligned about said rotor, said first and second mountingmembers are insertable into said first and second receivers, and aswitch means on said pump for detecting the insertion of said magneticfield source on said second mounting member into said second receiverand wherein said switch means enables said pump to rotate said rotor todeliver fluid to a patient when said second mounting member is detectedin said second receiver.
 5. A medical fluid delivery system fordelivering medical fluid to a patient comprisinga fluid delivery sethaving a fluid reservoir section, a drip chamber in fluid communicationwith the fluid reservoir section, a flexible tubing section adapted tobe mounted in a predetermined configuration on a fluid deliveryapparatus, a mounting member having a magnetic field source thereon andan elongate tubing section adapted to be placed in fluid communicationwith a patient, a peristaltic pump having a rotary member and first andsecond receiving members thereon wherein said drip chamber is mountableon said first receiving member and said mounting member is mountable onsaid second receiving member, a switch means on said peristaltic pumpfor enabling the operation of said rotary member in a first state anddisabling operation of said rotary member in a second state, said dripchamber and mounting member being arranged in a predeterminedconfiguration on said fluid delivery set adjacent to said flexibletubing section such that when said flexible tubing section is alignedabout said rotor in a predetermined configuration and said drip chamberis inserted into said first receiving member and said mounting member isinserted into said second receiving member, said flexible tubing sectionis aligned about said rotary member in an operative contacting relationwith said rotary member to allow the peristaltic pump to deliver medicalfluid at a controlled rate to a patient, and wherein an enabling meanson said second receiving member switches said switch means from saidsecond state to said first state to enable operation of said rotarymember on said peristaltic pump when said magnetic field source isdetected by said enabling means.
 6. A fluid delivery apparatus for thedelivery of a medical fluid to a patient, comprisinga peristaltic pumphaving a rotary member and first and second receivers thereon, a switchmeans on said peristaltic pump for enabling the operation of said rotarymember in a first state and disabling operation of said rotary member ina second state and wherein said switch means is normally in the secondstate, said second receiver having a magnetic field sensitive sensoradjacent thereto in operative communication with said switch means, afluid delivery set including first, second and third tubing sections, adrip chamber and a mounting member having a magnetic field sourcethereon wherein said first tubing section provides fluid flowcommunication between a fluid reservoir and said drip chamber andwherein said second tubing section provides fluid flow communicationbetween said drip chamber and said mounting member and wherein saidthird tubing section provides fluid flow communication between saidmounting member and a patient, said second tubing section beingsufficiently flexible so as to be operatively aligned about said rotarymember when said fluid delivery set is operatively mounted on saidperistaltic pump, said drip chamber and said mounting member beingspaced apart a predetermined distance on said fluid delivery set suchthat when said second tubing section is operatively aligned about saidrotary member, said drip chamber is insertable into said first receiverand said mounting member is insertable into said second receiver, andwherein said magnetic field sensitive sensor activates said switch meansfrom the second state to the first state in response to the detection ofsaid magnetic field source in said second receiver to enable theoperation of the rotary member to deliver fluid to a patient at acontrolled rate.
 7. A fluid delivery set for the delivery of a medicalfluid to a patient at a flow rate controlled by a rotor of a peristalticpump having a magnetic field sensor and first and second receivingmembers oriented for receiving portions of and mounting said fluiddelivery set in a predetermined and operation activating alignment aboutthe rotor of the peristaltic pump, the fluid delivery set comprising:aflexible tubing section having the first and second ends and havingsufficient flexibility to be adapted to be stretched in thepredetermined alignment about the rotor of the peristaltic pump, a dripchamber in fluid communication with said first end of said tubingsection, said drip chamber including a chamber section dimensioned andadapted to be removably mountable in the first receiving member whensaid tubing section is placed in the predetermined alignment about therotor of the peristaltic pump, and a mounting member in fluidcommunication with said second end of said tubing section, said mountingmember including a shoulder section and a magnetic field sourcedimensioned and adapted to be removably mountable in the secondreceiving member when said tubing section is placed in the predeterminedalignment about the rotor of the peristaltic pump, said magnetic fieldsource being positioned on said mounting member to be mountable inoperational proximity to the magnetic field sensor of the peristalticpump when said tubing section is in the predetermined alignment aboutthe rotor of the peristaltic pump to thereby activate the operation ofthe peristaltic pump.
 8. The fluid delivery set of claim 7 wherein saidmagnetic field source is toroidally shaped and substantially enclosed inthe second receiving member of the peristaltic pump when said tubingsection is placed in the predetermined alignment about the rotor of theperistaltic pump.
 9. A fluid delivery set for the delivery of a medicalfluid to a patient from a source of medical fluid at a flow ratecontrolled by a rotor of a peristaltic pump having a magnetic fieldsensor and first and second receiving members oriented for receivingportions of and mounting said fluid delivery set in a predetermined andoperation-activating alignment about the rotor of the peristaltic pump,the fluid delivery set comprising:a flexible first tubing section havingfirst and second ends and having sufficient flexibility to be adapted tobe stretched in the predetermined alignment about the rotor of theperistaltic pump, a second tubing section having first and second ends,said first end adapted to be placed in fluid communication with a sourceof medical fluid, a drip chamber having first and second ends, saidfirst end in fluid communication with said second end of said secondtubing section and said second end of the drip chamber in fluidcommunication with said first end of said first tubing section, saiddrip chamber dimensioned and adapted to be removably mountable in thefirst receiving members when said first tubing section is placed in thepredetermined alignment about the rotor of the peristaltic pump, amounting member in fluid communication with said second end of saidfirst tubing section, said mounting member including a magnetic fieldsource dimensioned and adapted to be removably mountable in the secondreceiving member when said first tubing section is placed in thepredetermined alignment about the rotor of the peristaltic pump, saidmagnetic field source being positioned on said mounting member to beadapted to be in operational proximity to the magnetic field sensor ofthe peristaltic pump when said first tubing section is in thepredetermined alignment about the rotor of the peristaltic pump tothereby activate the operation of the peristaltic pump, and a thirdtubing section having a first end in fluid communication with saidmounting member and a second end adapted to deliver medical fluid to apatient.